The present invention relates to a correction method of a feeding amount of a conveyance belt and to an inkjet recording apparatus employing the correction method of a feeding amount of a conveyance belt.
As an inkjet recording apparatus wherein ink drops are jetted from an ink jet head on a recording medium to be printed, there has been known one wherein a recording medium is conveyed by a conveyance belt of an endless type that is trained about plural rollers.
This conveyance belt is usually formed to be in an endless form by combining both ends of a belt-shaped belt member to be in a serrated form, so that both ends may be aced and spliced. In this thermal fusion splicing, both end portions of the belt member are pressed while they are fused. Therefore, the spliced portion thus spliced receives heat and pressure in the case of splicing, and its physical properties are changed, resulting in the phenomena where hardness and thickness of the spliced portion are different from those of other potions of the conveyance belt.
When a recording medium is conveyed by the conveyance belt having this spliced portion, when the spliced portion touches a roller, a difference of an amount of elongation from other portions of the belt is caused, and therefore, a feeding amount of the conveyance belt is fluctuated, resulting in troubles that an amount of conveyance for a recording medium is fluctuated.
Incidentally, it is also possible to manufacture a conveyance belt in an endless type, which, however, is not preferable because the manufacturing cost is high.
As a method for solving the aforesaid troubles, there have been suggested a method to detect the spliced portion to avoid sending of a recording medium and image forming in the spliced portion (for example, see Unexamined Japanese Patent Application Publication No. 2004-115176) and a method to detect a speed of the conveyance belt from rotation of a roller and to control speed fluctuation of the conveyance belt in the case of image forming by correcting image forming timing in the case when a reference position on the conveyance belt passes through the bottom part of an inkjet head, based on the aforesaid detection (for example, see Unexamined Japanese Patent Publication No. 2005-305919). In addition, there have been suggested methods to detect sheet-feeding errors of the conveyance belt and to control sheet-feeding errors by correcting encoder pulse to drive motor based on the results of the aforesaid detection by detecting an amount of conveyance for a recording medium from rotations of a roller and by confirming banding (white streaks and black streaks) by printing of plural-colored test patterns (for example, see Unexamined Japanese Patent Application Publication No. 2003-11345 and Japanese Patent Application Publication No. 3876654).
However, in the method described in Unexamined Japanese Patent Application Publication No. 2004-115176, it was impossible to print on a recording medium, because a fluctuation of a feeding amount of a conveyance belt in the case when the spliced portion touches the upper portion of the roller has not been controlled. Further, in the case of the methods described in Unexamined Japanese Patent Publication Nos. 2005-305919 and 2003-11345, and Japanese Patent Publication No. 3876654, fluctuations of feeding amount caused by a difference of an amount of elongation of the aforesaid conveyance belt cannot be detected by rotation of the roller, although speed fluctuations of the conveyance belt or sheet feeding errors are controlled based on the detection of rotations of the roller. In other words, fluctuations of feeding amount caused by distributions of hardness and thicknesses represented by the spliced portion and the other portions have not been controlled, because a feeding amount of the conveyance belt and an amount of rotation of the roller are not necessarily the same.
The present invention has been achieved in view of the aforesaid situation, and its objective is to provide a method of correcting a feeding amount of the conveyance belt that can control fluctuations of a feeding amount caused by distributions of hardness and thickness of the conveyance belt, and to provide an inkjet recording apparatus.